In a typical wireless communication network, an area is divided geographically into a number of cells and cell sectors, each defined by a radio frequency (RF) radiation pattern from a respective base transceiver station (BTS). Within each cell sector, the BTS's RF radiation pattern provides an air interface through which mobile stations (or terminals) may communicate with the BTS. The BTSs in the cells in turn couple to a base station controller (BSC), which then couples to a telecommunications switch or gateway, such as a mobile switching center (MSC) or packet data serving node (PDSN) for instance. The switch or gateway may then couple to a transport network, such as a public switched telephone network (PSTN) or a packet-switched network (e.g., the Internet). Conveniently with this arrangement, when a mobile station is positioned within a given cell sector, the mobile station can communicate with entities on the transport network via a communication path comprising the RF air interface, the BTS, the BSC, the switch or gateway, and the transport network. The combination of network entities that provides a connection between the mobile station and the transport network may be considered a radio access network (RAN).
The RF air interface of any given cell sector is typically divided into a plurality of channels for carrying communications between the mobile stations and the BTS. For example, the RF air interface may include (i) a plurality of forward-link channels (e.g., pilot channels, sync channels, paging channels, and forward-traffic channels) for carrying communications from the BTS to the mobile stations, and (ii) a plurality of reverse-link channels (e.g., access channels and reverse-traffic channels) for carrying communications from the mobile stations to the BTS.
A paging channel of the RF air interface is typically used for signaling mobile stations, setting up communications with mobile stations, and delivering small messages to mobile stations. Mobile stations that are in dormant mode (i.e. not assigned a traffic channel) monitor the paging channel periodically instead of continuously in order to reduce power consumption.
In a Code Division Multiple Access (CDMA) wireless communication network, the paging channel is typically divided into a number of time slots (e.g., 32 or 64 slots) of a specific duration (e.g., 80 ms). The group of time slots is defined as a slot cycle, and the slot cycle repeats continuously. For example, a paging channel with 32 slots, each 80 ms in duration, will have a slot cycle of 2.56 seconds. Therefore, each individual slot repeats every 2.56 seconds.
Several sectors may define a paging area, and when a mobile station registers with the network in a given paging area, the RAN assigns the mobile station to one of the time slots (generally distributing the mobile stations evenly among all of the time slots). Mobile stations assigned to the same time slot constitute a slot group. When the RAN has a page message to send to a particular mobile station, it sends the page during the mobile station's assigned time slot. To receive pages from the RAN, a mobile station only needs to wake up only during its assigned slot in order to listen for the page; it can remain asleep for the rest of the slot cycle. In the above example, a mobile station wakes up for 80 milliseconds every 2.56 seconds to listen for pages on the paging channel. This saves a considerable amount of battery life compared to continuously monitoring the paging channel.
Rather than sending separate page messages to each mobile station, the RAN may broadcast a General Page Message (GPM) to all mobile stations in a particular slot group. The GPM includes one or more individual page messages or records. Each page record identifies a particular mobile station and contains a page message for that particular mobile station. Like a record in a database, a page record is comprised of many fields that contain important information for the mobile station. For example, some fields define the page type, while others include the page message or other instructions for the mobile station. One field in particular is the terminal identifier field. This is the field that a mobile station searches when determining which page record in a GPM is intended for that mobile station. Every mobile station in the RAN's global coverage area is associated with a globally unique terminal ID. When the RAN has a page message to send to a particular mobile station, the RAN creates a page record containing the page message, and encodes the globally unique terminal ID as a bit string into the terminal identifier field. To receive a page message, the mobile station (i) wakes up during its time slot, (ii) receives the GPM, and (iii) searches the GPM for a page record with a terminal identifier field that matches the mobile station's terminal ID.